Request: allow slug-relative route self@/route in Filepicker (destination)

[yankl]

When using the filepicker you can use @path:/route. It's also possible to use self@/path to go to a subdirectory relative to the current page. However, then it is picky about, e.g., there is a numerical prefix or not on the directory name. It would be great if there were an option to pick a (slug?) route relative to the current page.